Field of the Invention
The present invention relates to a roller for electrophotography for use in an electrophotographic image forming apparatus and a production method thereof. The present invention also relates to an electrophotographic image forming apparatus.
Description of the Related Art
An electrophotographic image forming apparatus usually includes an image bearing member like an electrophotographic photosensitive member, a charging member that charges the surface of the image bearing member, an exposure apparatus in which the surface of the image bearing member is irradiated with light modulated depending on image information, a developing member that performs development by a developer (toner) to form a visible image (toner image) on the image bearing member, and a transfer member that transfers the visible image on the image bearing member, to a recording material.
In the electrophotographic image forming apparatus, a roller for electrophotography like a transfer roller, which transfers the toner image from the surface of the image bearing member to the surface of the recording material, is used. Such a roller for electrophotography includes a roller for electrophotography including an electro-conductive mandrel and a surface layer that is formed on the outer periphery of the electro-conductive mandrel and that includes an electro-conductive foam.
Japanese Patent Application Laid-Open No. 2010-211020 discloses use of a rubber composition in such an electro-conductive rubber layer of the transfer roller, the composition having a sea-island structure in which an island phase of a rubber component B mainly including an epichlorohydrin rubber is dispersed in a sea phase of a rubber component A mainly including acrylonitrile-butadiene, wherein the area ratio of the island phase, and the proportion of an island phase having a predetermined shape in the entire island phase area are in specific ranges. Then, the following is disclosed: such a transfer roller, in which electro-conductivity of the rubber layer depends on electro-conductivity of the polymer chain itself of the rubber, thus exerts the effect of less causing other member in abutment with the transfer roller to be contaminated due to bleeding of an ion conductive agent onto the surface of the transfer roller.
The present invention is directed to providing a roller for electrophotography that has a high electro-conductivity, namely, a low electric resistance value, and that is still further reduced in contaminating property of other member, as well as a method for producing the roller for electrophotography. The present invention is also directed to providing an electrophotographic image forming apparatus that serves for formation of a high-quality electrophotographic image.